Plate heat exchanger

ABSTRACT

The invention relates to a plate heat exchanger that consists of several pieces of sheet metal that are arranged parallel to one another, that are at least partially corrugated and that form a considerable number of heat-exchange passages. A header creates a flow connection among at least some of the heat-exchange passages. At least two parts ( 1, 2, 3 ) of the plate heat exchanger consist of metallic materials that cannot be welded to one another.

SUMMARY OF THE INVENTION

[0001] An object of this invention is to provide an improved plate heatexchanger. Another object is to provide a novel header construction.Upon further study of the specification and appended claims, otherobjects of the invention will become apparent.

[0002] The objects are achieved according to the invention by a plateheat exchanger of the above-mentioned type, in which at least two partsof the plate heat exchanger comprise metallic materials that cannot bewelded to one another on an industrial scale.

[0003] Consequently, the plate heat exchanger according to the inventionare not limited to only one material, but rather require at least twodifferent metallic materials. The two different materials can be adaptedto the specific operational requirements of the individual components ofthe plate heat exchanger. Thus, for components that are exposed to anelevated compression stress, for example for the header of the heatexchanger, a metal is used that has a higher strength than the materialused for the heat exchanger block.

[0004] The two parts of the heat exchanger that comprises differentmetals or different metal alloys are preferably bonded integrallytogether. Even at high stresses within the plate heat exchanger, thebond should provide a stable, durable and tight connection. By usingfasteners which provide clamping or frictional connections, for exampleby screwing two components together, it is very difficult, owing to thedifferent thermal coefficients of expansion, to connect the componentstightly enough together so that the sealing of the flow paths in theplate heat exchanger is ensured permanently.

[0005] As mentioned above, it is often very difficult to provide aconnection of different metallic materials that can withstand thethermal stresses of a heat exchanger. Fasteners which provide a clampingor frictional connection often are not satisfactory because of thermalexpansion, and a more stable material is not possible partially becauseof the different properties of the metals that are involved. Thus, forexample, aluminum and steel cannot be welded to one another at least onan industrial scale, and in the context of this invention such metalsare considered non-weldable to each other.

[0006] It has therefore proven advantageous to provide an intermediatepiece between the two components which piece comprises at least twodifferent metals or metal alloys similar to the various metallicmaterials in the components that are to be connected to one another. Themetals of the intermediate piece are selected in such a way that atleast two surfaces of the intermediate piece are present, which in eachcase can be connected to one of the two components in a tight andheat-resistant manner. Each component is preferably welded to one of thetwo sides of the intermediate piece which has the same type of metal.

[0007] The intermediate piece can be produced in various conventionalways while maintaining satisfactory bonding strengths. Individual metallayers of the intermediate piece can be applied, for example, by thermalcoating. Preferably, the intermediate piece is produced by explosiveplating of two or more metals. To this end, two or more metal plates areplaced on one another and are provided with a layer of explosivesubstance. The pressures that are produced in an explosion bring themetals in the area of the boundary layer between two metal plates intothe plastic state, by which a durable and tight connection is created.

[0008] The invention is suitable especially for plate heat exchangers inwhich the sheets or the entire heat exchanger blocks consist essentiallyof aluminum. To date, headers made of aluminum are also attached to suchheat exchanger blocks, which are accompanied, however, by theabove-mentioned strength problems. Headers made of steel, especiallyCr—Ni steel, low-temperature steel or C-steel, are preferably used. Thehigher strength values of the steel headers allow larger header andsupport dimensions. The previously required double header with multiplesupports or even the parallel arrangement of several plate heatexchangers is avoided or at least reduced. As a result, it is no longernecessary to have costly and difficult intermediate tubing betweenindividual heat exchanger blocks.

[0009] Steel headers also provide additional cost advantages in the caseof the tubing. For pipelines between different plate heat exchangers,which can now be made of steel instead of aluminum, smaller wallthicknesses in comparison to aluminum can now be provided owing to thehigher strength of steel. The costs and the difficulty of the weldingare significantly reduced. The steel pipelines from the plate heatexchangers that lead from or to the latter can be welded directly to thesupports of the header and no longer must be connected to the latter viaflange connections.

[0010] The headers are fastened to the heat exchanger block via anintermediate piece that comprises a composite material that preferablycontains at least aluminum and steel.

[0011] The intermediate piece is excised from a plate of the compositematerial, which corresponds in size to approximately the contact surfacebetween the header and the heat exchanger block. One opposing side ofthe intermediate piece consists essentially of aluminum and the otheropposing side consists essentially of steel. The intermediate piece iswelded to the header on its steel side and then the thus prepared novelheader construction is welded on the aluminum side to the heat exchangerblock.

[0012] The intermediate piece provides for a slightly elevated positionof the header, thereby making the weld more readily accessible andfacilitating the welding. Moreover, the distance between two adjacentheaders can be reduced, which results in a reduction in size of the heatexchanger block.

[0013] The heat exchanger according to the invention can be used in thetemperature range of for example, between −270° C. and +200° C. and atan operating pressure of for example, from vacuum conditions to over 100bar. In the entire range of use, the gas sealing property and stabilityof the heat exchanger are ensured.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The invention as well as other details of the invention areexplained in more detail below based on the embodiments that aredepicted in the drawings, wherein:

[0015]FIG. 1 diagrammatically depicts the structure of a plate heatexchanger according to the invention, and

[0016]FIG. 2 depicts the composite material in detail.

[0017] A heat exchanger block comprises a housing 1 containingcorrugated and flat aluminum sheets conventionally soldered together ina soldering furnace. The heat-exchange passages formed between thesheets are closed to the outside by cover strips forming the housing. Anarea 2 is used as an intake opening to the heat-exchange passages. Aheader 3, which is provided with a connecting piece 4, creates a flowconnection between the supply line for one of the fluids that is toundergo heat exchange, not shown, through the connecting piece 4, to theheat-exchange passages.

[0018] A frame 5 is welded to header 3, and the thus prepared header isthen welded gastight to intake opening 2. Frame 5 is depicted moreprecisely in FIG. 2. Frame 5 consists essentially of an aluminum layer 6and a steel sheet 7, which are connected to one another using anexplosive plating process. The thus produced plate heat exchange isdistinguished by high strength and is preferably used in high-pressureapplications. For further details of the explosive plating process,reference is made to the literature, for example, the attached brochureby Dynamit Nobel entitled “Dynaplat Verbindungen durch Sprengstoff.

[0019] In the specification and the following claims,

[0020] Cr—Ni steel is any steel alloyed with chromium and nickel;

[0021] low temperature steel is any steel alloyed for low temperatureapplication; and

[0022] C-steel is any unalloyed steel.

[0023] The preceding examples can be repeated with similar success bysubstituting the generically or specifically described reactants and/oroperating conditions of this invention for those used in the precedingexamples. Also, the preceding specific embodiments are to be construedas merely illustrative, and not limitative of the remainder of thedisclosure in any way whatsoever.

[0024] The entire disclosure of all applications, patents andpublications, cited above and below, and of corresponding Germanapplication 10022595.0, are hereby incorporated by reference.

[0025] From the foregoing description, one skilled in the art can easilyascertain the essential characteristics of this invention, and withoutdeparting from the spirit and scope thereof, can make various changesand modifications of the invention to adapt it to various usages andconditions.

1. Plate heat exchanger that consists of several pieces of sheet metalthat are arranged parallel to one another, that are at least partiallycorrugated and that form a considerable number of heat-exchangepassages, as well as at least one header that creates a flow connectionamong at least some of the heatexchange passages, characterized in thatat least two parts (1, 2, 3) of the plate heat exchanger consist ofmetallic materials that cannot be welded to one another.
 2. Plate heatexchanger according to, wherein two parts (1, 2, 3) are connectedintegrally together.
 3. Plate heat exchanger according to claim 2,wherein an intermediate piece (5) that consists of two different metalsor metal alloys (6, 7) is found between the two parts.
 4. Plate heatexchanger according to claim 3, wherein intermediate piece (5) isproduced by explosive plating.
 5. Plate heat exchanger according to oneof claims 1 to 4, wherein sheets (2) consist of aluminum.
 6. Plate heatexchanger according to one of claims 1 to 5, wherein header (3) consistsof steel, especially Cr—Ni steel, low-temperature steel or C-steel. 7.Plate heat exchanger according to one of claims 3 to 6, whereinintermediate piece (5) contains aluminum and steel.